With the advent of anti-lock brake systems, automatic transmissions, semi-automatic transmissions, electronically enhanced braking systems and electronic fuel control systems, it has always been known that the operation of these systems may be enhanced if information relating to the vehicle's true acceleration is available and whether or not the vehicle is ascending or descending a road grade is known.
Gaehe, in U.S. Pat. No. 3,752,251, discloses a grade sensor for use in conjunction with a wheel braking system. The grade sensor disclosed by Gaehe is designed to be insensitive to acceleration and deceleration of the vehicle. Shattock, in U.S. Pat. No. 3,588,188, discloses a pendulum-type acceleration sensor for detecting the acceleration and deceleration of a vehicle for a braking system, while Klatt teaches how information indicating whether the vehicle is traveling uphill or downhill can be used to control an automatic transmission. Klatt teaches the use of changes in the engine's torque to make this determination.
Disclosed herein is a grade angle and acceleration sensor which can provide to anti-lock braking systems, automatic transmissions and electronically controlled braking systems both the grade angle of the road being traversed and the true acceleration or deceleration of the vehicle along the roadway.